Metal bioavailability, toxicity, and ecological risk due to sediments of a lately rehabilitated lake (Mariut, Egypt).

Sediments from Lake Mariut, Egypt, after its rehabilitation, and its anoxic diverted polluted drains were subjected to five sequential steps to define different geochemical fractions of eight studied metals. Results cleared out that 30-50% of its total Cd and total Co contents are easily bioavailable with a high-risk assessment code (RAC) to enter the food chain in the lake basin. Whereas Cu and Fe are safe and the remaining studied metals, i.e., Mn, Zn, Pb, and Cr are of medium risk for the environment. Individual contamination factor (ICF) is high (> 6) for all the studied metals except for Fe and Cu which are tightly held in sediments confirming their safeness to biota. Cadmium accounted for > 94% of the total risk in the study area. Metal pollution loading (MPL) from the sediments was found in the order: Fe > Mn > Zn > Pb > Cu > Cr > Co > Cd.

Possible human health risk of some heavy metals from consumption of tilapia fish from Lake Mariut, Egypt.

Lake Mariut Main Basin (MB) is not only one of the three basins composing Lake Mariut (LM) but is also the main source of the popular tilapia fish to Alexandrian people. Unfortunately, this basin was consistently for about 50 successive years receiving a continuous discharge of agricultural, sewage, and industrial effluents. This has led to contamination of the flesh of its tilapia fish living there particularly with some toxic heavy metals like Cd and Pb. Lately, in 2010, a rehabilitation program was adopted and carried out to save this vital MB from such intensive pollution. This had been achieved by diverting all those polluting sources. The present work is made after elapsing about 7 years from the diversion process date, to assess and evaluate the levels of those two metals (in addition to the other four one's Fe, Cu, Cr, and Zn) in the edible flesh part besides the liver and gills of this fish (Nile tilapia spec., Oreochromis niloticus), and in ambient water of this restored basin to measure the efficiency of the rehabilitation program on quality of endogenous fish. A simultaneous parallel sampling program was also commenced for the other two basins of LM. The obtained results revealed that the concentration level of the studied metals in each of the muscles of the fish and the ambient water of the restored MB becomes now not only almost alike the metal levels of the corresponding compartments of the other two basins of LM, but also they became at concentration levels lay below those of their counterpart permissible limits in fish and water recommended by national and international standards. Health risk assessment indices: bioaccumulation factor (BAF), metal pollution index (MPI), estimated daily intake (EDI), hazardous index (HI), and relative risk (RR) for the present case were estimated, assessed, and subsequently evaluated. All are referring to a fact that MB is currently in good environmental condition and producing safe fish for human consumption.

Water quality assessment and phosphorus budget of a lake (Mariut, Egypt) after diversion of wastewaters effluents.

The water quality of Lake Mariut has been deteriorated for about 5 decades due to continuous discharge of agricultural, municipal, and industrial wastes from Alexandria City and the adjacent land. During the past two decades, some steps were taken for rehabilitation of the lake through primary treatment of the discharged wastes and insulation of the polluted wastewater of QD from the water body in the main basin of the lake. Several parameters of water quality at the surface and near bottom were measured at twelve locations during winter (January) and summer (August) of 2013 and 2014. The present study revealed that the lake water appeared to be well aerated but still containing high concentrations of N and P and suffering hyper-eutrophic conditions. The water quality index (WQI) reflected medium condition in the lake and bad condition in the diverted drains. The P-budget calculation displayed that TP input into the LMMB from UDus and resuspension process from sediments exceeded the output by out flowing at UDds and settling.

Exposure to ZnO nanoparticles alters neuronal and vascular development in zebrafish: Acute and transgenerational effects mitigated with dissolved organic matter.

Exposure to ZnO-nanoparticles (NPs) in embryonic zebrafish reduces hatching rates which can be mitigated with dissolved organic material (DOM). Although hatching rate can be a reliable indicator of toxicity and DOM mitigation potential, a fish that has been exposed to ZnO-NPs or any other toxicant may also exhibit other abnormal phenotypes not readily detected by the unaided eye. In this study, we moved beyond hatching rate analysis to investigate the consequences of ZnO-NPs exposure on the nervous and vascular systems in developing zebrafish. Zebrafish exposed to ZnO-NPs (1-100 ppm) exhibited an array of cellular phenotypes including: abnormal secondary motoneuron (SMN) axonal projections, abnormal dorsal root ganglion development and abnormal blood vessel development. Dissolved Zn (<10 kDa) exposure also caused abnormal SMN axonal projections, but to a lesser extent than ZnO-NPs. The ZnO-NPs-induced abnormal phenotypes were reversed in embryos concurrently exposed with various types of DOM. In these acute mitigation exposure experiments, humic acid and carbohydrate, along with natural organic matter obtained from the Suwannee River in Georgia and Milwaukee River in Wisconsin, were the best mitigators of ZnO-NPs-induced motoneuron toxicity at 96 h post fertilization. Further experiments were performed to determine if the ZnO-NPs-induced, abnormal axonal phenotypes and the DOM mitigated axonal phenotypes could persist across generations. Abnormal SMN axon phenotypes caused by ZnO-NPs-exposure were detected in F1 and F2 generations. These are fish that have not been directly exposed to ZnO-NPs. Fish mitigated with DOM during the acute exposure (F0 generation) had a reduction in abnormal motoneuron axon errors in larvae of subsequent generations. Therefore, ZnO-NPs exposure results in neurotoxicity in developing zebrafish which can persist from one generation to the next. Mitigation with DOM can reverse the abnormal phenotypes in an acute embryonic exposure context, as well as across generations, resulting in healthy fish.

Zinc oxide nanoparticle toxicity in embryonic zebrafish: Mitigation with different natural organic matter.

Exposure experiments were conducted to evaluate the influence of dissolved organic matter (DOM) on the toxicity of ZnO-NPs (10-30 nm) and dissolved Zn at sub-lethal doses (50 and 5 ppm, respectively) to zebrafish (Danio rerio). Humic acid, alginic acid, bovine serum albumin and various natural DOM isolated from rivers as the Milwaukee River-WI (NOMW), Yukon River-AK (NOMA) and Suwannee River-GA DOM (NOMS) were used to represent humic substances (HA), carbohydrates (CHO), proteins (PTN), and natural organic matter (NOM), respectively. Initial experiments were carried out to confirm the toxic effect of ZnO-NPs at 50 ppm, followed by mitigation experiments with different types and concentrations of DOM (0.4-40 mg-C/L). Compared to 0% hatch of 50 ppm ZnO-NPs exposed embryos at 72 h post fertilization (hpf), NOMS, NOMW and HA had the best mitigative effects on hatching (53-65%), followed by NOMA, CHO and PTN (19-35%); demonstrating that the mitigation effects on ZnO-NPs toxicity were related to DOM's quantity and composition. At 96 hpf, 20% of embryos exposed to 50 ppm ZnO-NPs hatched, 100% of embryos reared in embryo medium hatched, and close to 100% of the embryos hatched upon mitigation, except for those mitigated with PTN which had less effect. Dissolved Zn (5 ppm) also exhibited the same toxicity on embryos as ZnO-NPs (50 ppm). However, in the presence of HA, NOM and CHO, the hatching rates at 72 and 96 hpf increased significantly compared to 5% hatch without DOM. The overall mitigation effects produced by DOM followed the order of HA ≥ NOMS > NOM (A&W) > CHO >> PTN, although specific mitigation effects varied with DOM concentration and functionalities. Our results also indicate that the toxicity of ZnO-NPs to embryos was mostly derived from NPs although dissolved Zn released from ZnO-NPs also interacted with embryos, affecting hatching, but to a less extent.

Assessment of water quality in Alamein Marina Recreational Lagoon.

BACKGROUND: Alamein Marina Lagoon is one of six lagoons, lying on the Egyptian Mediterranean Coast. Between 1988 and 1995, a large-scale recreational compound called Alamein Marina Touristic Village was established to contain most of these lakes. The study aims to assess the quality of Alamein Marina Lagoon water in an attempt to evaluate the environmental impact of the touristic summer activities on the lake and to determine at what level this recreational lagoon stands as a healthy resort, among the other resorts around the Mediterranean Sea Basin. MATERIALS AND METHODS: Fourteen sampling stations were chosen to present the four sub-basins of the lagoon and its outlets on the Mediterranean Sea. Physical, chemical, and bacteriological characteristics of the lagoon water were determined. RESULTS: Lagoon water pH was found to range between 6.8 and 7.9. Dissolved oxygen, biochemical oxygen demand, nitrates and phosphates were 6.5 mg/L, 1 mg/L, 0.5 µg/L, and 3.8 µg/L respectively. Fecal coliform were not detected in all sampling stations. CONCLUSION: Alamein Marina water characteristics were complying with the standards set by Egyptian legislations concerning recreational water all over the study period. They were also complying with the levels set by different international organizations such as the WHO and Blue Flag. Besides, by calculating the water quality index for Alamein Marina Lagoon and its four sub-basins, water was found to be of an 'excellent' quality.

Approaches to environmental restoration of a polluted harbour with submerged archaeology: the Alexandria case study.

Many invaluable underwater buildings of archaeological interest in Alexandria were discovered in 1996 at different sites in the Eastern Harbour of Alexandria. There is a belief that the best way to protect these invaluable heritages is to transfer them to an underwater park or museum. Obviously, the execution of such a project depends essentially upon the water quality (including water transparency) improving in the future. The harbour is presently polluted by discharge of wastewater effluents from different sources. It has recently been decided to restore this important coastal area through: (1) stopping the direct discharge of wastewater effluents into this semi-enclosed harbour in 1993 and (2) gradually reducing the discharge of the municipal wastewater through marine outfalls at two sites lying at the outer sides of the harbour. Zero discharge is expected to be effective by the end of the year 2001. The present work, therefore, is a follow up of the study of water quality in the harbour after 1993: in 1996 and 1999-2000. The water quality of an open sea reference station was also studied for comparison. The results reveal occurrence of an improvement of the environmental conditions in the harbour. The water has turned from being eutrophic to mesotrophic. The harbour is expected to become meso/oligotrophic as soon as the complete cessation of the discharge from the two outside sources is attained.